Plasma Concentrations of Testosterone in the Male Dog and Plasma Testosterone Profile Following Single Intramuscular Injection of HCG

The spontaneous variation in plasma testosterone was studied in 4 dogs in a 24 h period. Blood samples were taken with 1½ h interval. A variation of 26–62 % was found in the plasma testosterone concentration and the values ranged from 2.7–15.6; 0.7–10.4; 4.2–17.3; 8.7–23 nmol/l. No effect of intramuscular injection of 150 i.u. HCG could be seen on the plasma testosterone levels in samples taken 5, 10, 20 or 30 min post injection. Thereafter plasma testosterone levels increased to reach levels equal to peak concentration in the control period 1½ h post injection. The variation in the plasma testosterone concentration 1½, 3 and 4½ h post HCG injection was reduced to 8.95 ± 2.8 % (mean ± s). Plasma testosterone in a sample taken 3 h after HCG injection might thus be indicative of a Leydig cell dysfunction in the dog. An additional increase (P < 0.001) in plasma testosterone levels was observed 21–30 h post injection. Thereafter levels of testosterone fell to pre-stimulation values.     

Long-term effect of HCG on plasma testosterone in bulls.

The spontaneous diurnal variation of peripheral plasma testosterone concentrations in four bulls was established and then the long-term effect of a single intravenous or intramuscular injection of HCG on testosterone levels was studied. Intravenous and intramuscular HCG injections produced, within 1/2 hr and 3 hr, respectively, a rapid rise of testosterone to levels equivalent to the highest values seen in the diurnal pattern. A second increase of up to x2 to x3 the highest values of the diurnal cycle was observed 2 days after the injection of HCG, and the testosterone level remained high for at least 3 to 4 days after plasma levels of HCG were no longer detectable. The pattern of diurnal variation after HCG revealed an attenuation of the extensive spontaneous variation and high levels with only slight fluctuations were maintained.     

Fertility, ovulation and maturation of eggs in mares injected with HCG

Pony mares were observed from January to August for incidence of oestrus, duration of oestrus, length of the oestrous cycle and for ovulation and fertility after injection of HCG. From January to 15 May most mares showed oestrus but the duration of oestrus was quite variable and few mares ovulated in response to HCG. From 15 May to 17 August oestrous cycles were more regular and ovulation was induced within 40-50 h by an intramuscular injection of 1500-5000 i.u. HCG. Pregnancy was established by one mating at a fixed time after HCG in 20 of 69 mares. Degenerate eggs were recovered from the oviducts of anoestrous recently ovulated, mated, unmated and pregnant mares. The first polar body was formed before ovulation in 2 eggs and had not formed in 2 recently ovulated eggs flushed from the oviduct. The second polar body formed after sperm penetration 10-12 h after ovulation. After formation of pronuclei, the first cleavage division occurred at 20 h and the second at 32 h after ovulation. Oestrus was inhibited by progesterone administered by vaginal devices but occurred within 1-3 days in 12 of the 20 mares after withdrawal of the devices.     

醋酸棉酚对大鼠睾丸HCG反应性及其受体功能的影响

给大鼠灌服醋酸棉酚30 mg/kg/d,每周6次,持续4周。给药2周后,血浆睾酮水平显著下降并持续至第4周,同时间质细胞呈萎缩性改变。醋酸棉酚明显抑制成年大鼠对HCG反应性,使睾丸LH/HCG受体亲和力下降,受体数目略有减少。结果提示,醋酸棉酚抑制大鼠睾丸酮的产生及降低成年大鼠睾丸对HCG的反应性,推测其机制是由于醋酸棉酚干扰了睾丸HCG受体功能而造成的。     

Characterization of LH and testosterone responses to intramuscular injection of GnRH in tropical postpubertal bulls

Five Zebu x British crossbred bulls 17 months of age and of uniform liveweight (320+/-3 kg) were used to study testosterone responses to single intramuscular doses of exogenous gonadotropin-releasing hormone (GnRH). The eight dose levels used were 0, 31.25, 62.5, 125, 250, 500, 1000, and 2000 ng GnRH/kg live weight. Plasma samples for hormone responses were collected at 30-minute intervals from zero to three hours and at one-hour intervals from three to seven hours postinjection. Luteinizing hormone (LH) and testosterone responses were measured as peak heights or as areas under response curves. Increasing the dosage of GnRH increased the time to reach the peak LH response, the height and duration of the response, and the area under the response curve. The maximum LH peak height was reached by the 1 mug/kg dose. In contrast to LH, testosterone responses reached the same peak heights (two hours postinjection of GnRH) for all doses of GnRH. The only effect of increased dosage was to increase the duration of response. Testosterone responses showed repeatable differences (P<0.01) between animals, but LH responses did not. It was demonstrated that the testosterone status of bulls can be accurately assessed by simply measuring testosterone in a single plasma sample collected two to three hours after the intramuscular injection of 100 mug or more (dose unimportant) of GnRH per bull.     

Ratios of serum concentrations of testosterone and progesterone from yearling bulls with small testes

Thirty crossbred bulls, 12 to 13 mo of age, were used to examine the relationship of testosterone and progesterone concentrations and testosterone: progesterone ratio to measurements of testicular function. Bulls were allotted to 1 of 2 groups based on scrotal circumferences (SC) as follows: the Small SC (n=20) group had scrotal circumference less than 28 cm while the Large SC (n=10) group had scrotal circumference greater than 28 cm. All bulls were administered GnRH (100 mug, im), and blood was obtained immediately prior to injection (t=0), 30 min after injection (t=30) and 2 to 3 h after injection (t=150). Serum was assayed for concentrations of testosterone and progesterone. Semen was evaluated for the percentage of morphologically normal spermatozoa. Testicular parenchyma was sectioned and stained, and 300 cross sections per testis of seminiferous tubules were examined under a light microscope and classified as either active (spermatocytes and spermatids present) or inactive (no spermatocytes or spermatids present). Although progesterone concentrations varied widely (range: 21 pg/ml to 1070 pg/ml), repeated measurements from individual bulls were highly correlated (r(2)=0.74) and did not change significantly (P > 0.1) in response to GnRH treatment. Small SC bulls had a higher percentage of inactive seminiferous tubules (P < 0.001) and a lower percentage morphologically normal spermatozoa (P < 0.001) than Large SC bulls, but no differences in testosterone or progesterone concentrations or in the ratio of testosterone: progesterone were detected. Mean serum testosterone concentration increased (P < 0.0001) by 30 min after GnRH treatment and continued to increase (P < 0.0001) through t=150 but did not differ (p > 0.1) between groups. Normal testosterone secretion in response to GnRH injection suggested that no biochemical lesions in the testosterone production pathway were present in bulls with very small scrotal circumference.     

Role of prostaglandin F2alpha in ovulation.

Using radioimmunoassay procedures, the levels of plasma, uterine and ovarian prostaglandin (PG) F2alpha, and those of plasma estradiol and progesterone were measured in intact, hysterectomized or ovariectomized immature female rats pretreated with PMS and subsequent HCG. Occurrence of ovulation was confirmed at 8 hours after the HCG administration not only in the intact rats but also in the hysterectomzied rats. The levels of plasma estradiol and progesterone, and of uterine and ovarian PGF2alpha rose with the PMS injection alone, but they did not reach the peaks before the HCG administration. Both plasma estradiol and uterine PGF2alpha showed a peak at 2 hours after the HCG injection. These peaks were antecedent 2 or 6 hours before the peaks of ovarian and plasma PGF2alpha, respectively. However, such increase of uterine PGF2alpha does not seem to be indispensable for ovulation, because ovulation could occur in the hysterectomized rats. The levels of ovarian PGF2alpha showed a high plateau from 4 to 8 hours after the HCG injection, and then rapidly decreased after ovulation. The levels of plasma PGF2alpha peaked not only in the intact rats but also in the hysterectomized rats at 8 hours after the HCG treatment. But in the ovariectomized rats, this plasma PGF2alpha peak at 8 hours disappeared and there was no statistical change of plasma PGF2alpha throughout the PMS-HCG treatment. Plasma progesterone gradually increased and reached the maximum at 10 hours after the HCG injection. These results conclude that the main source of increased plasma PGF2alpha during the ovulatory process induced with the PMS-HCG treatment is the ovary, and it is strongly suggested that a rapid increase of PGF2alpha in the ovary may play some important role(s) in the ovulatory process.     

Ovarian response to PMSG treatment in ewes immunized against oestradiol-17 beta

The effects of active immunization against oestradiol-17 beta on the ovarian response to pregnant mare serum gonadotrophin (PMSG) was investigated in Merino ewes. Immunized (79) and control (41) ewes were synchronized with intravaginal sponges, given either 750 or 1500 i.u. PMSG and then mated to rams or inseminated laparoscopically with fresh diluted semen. All control ewes mated naturally exhibited oestrus and 40 out of 41 control ewes ovulated. The ovulation rate was higher in the controls receiving 1500 i.u. PMSG than in those ewes which received 750 i.u. PMSG (10.2 v. 3.3). Immunization against oestradiol-17 beta resulted in antibody titres varying from 100 to more than 100 000 in plasma taken 1-4 days after mating. The ovarian response increased significantly in the lowest titre group (100-1000) in conjunction with stimulation with 1500 i.u. PMSG. In these ewes the ovulation rate increased over controls (16.7 v. 10.2) as did the total ovarian response, which includes follicles greater than 10 mm diameter (22.3 v. 11.1). The total ovarian response was also increased in those ewes given 750 i.u. PMSG which had titres in the 1000-10 000 and 10 000-100 000 range, but this was not accompanied by significant increases in the ovulation rate. In general, the higher titre levels (greater than 1000) were correlated with decreases in the proportion of ewes showing oestrus and ovulating and in the embryo recovery rate. The 1500 i.u. PMSG treatment group with the highest titres (greater than 10 000) also showed a significant drop in the ovulation rate as compared to the 1500 i.u. PMSG controls.     

Reproductive performance and productive traits of beef bulls selected for different levels of testosterone response to GnRH

In two separate studies, one with four Hereford-Shorthorn and one with three Zebu x British crossbred bulls, the efficacy of using the testosterone response to gonadotrophin-releasing hormone (GnRH; Lutal, Hoechst) to predict differences in reproductive performance was assessed. Young bulls (17 or 29 months of age) selected for low to high (3.1 to 10.3 ng/ml) peak plasma testosterone 2 to 2.5 hours after the intramuscular injection of GnRH (62.5 to 2000 ng/kg LWT) were each later individually joined with groups of 19 to 30 cows in which estrus had been synchronized. In both studies, the rankings of bulls for overall fertility (capable cows pregnant), for libido (estrous cows mounted), and for fertilizing ability (mounted cows pregnant) were in close agreement with rankings for testosterone responses to GnRH. In the Bos indicus bulls rankings for both reproductive performance and testosterone response to GnRH were repeatable when measured at two and four years of age. Other reproductive measurements (semen quality, scrotal circumference, pen-type serving capacity tests) were less reliable predictors of reproductive performance. Measurements of liveweight gains and parasite resistance indicated that bulls superior for these characteristics do not always have satisfactory reproductive performance. These studies suggest that the testosterone response to GnRH could be a useful test to ensure that bulls selected for productive traits have adequate reproductive potential.     

Plasma androstenedione after injections of dexamethasone and luteinizing hormone releasing hormone in young post-pubertal bulls

This study was performed on six French Friesian bulls (aged 12 months at the onset of the experiment) on two separate occasions, 3 months apart and lasting 2 days each time. On each of both occasions, three bulls were submitted on the first day to an i.m. injection of dexamethasone (DXM, 20 mg) 6 h priot to a Luteinizing Hormone Releasing Hormone (LH-RH) challenge (0.250 mg i.m.) and the three others (control animals) to LH-RH only. On the second day, they all received a single LH-RH injection. The treated animals then served as controls on the second occasion and the controls as DXM—LH-RH treated individuals. Blood samples were taken at hourly intervals before LH-RH treatment (for 5 h), then every 15 min (for 2.5 h), and afterwards, every hour for 3 h.Androstenedione concentrations were significantly enhanced after LH-RH challenge in a similar manner on days 1 and 2 within groups, but the relative magnitude of the response in terms of area under the curve (ng/ml of plasma × 150 min) was lower in the DXM—LH-RH treated group than in the controls. In addition, the individual correlation between the testosterone and androstenedione responses was significant (P <0.05) in those animals treated but not in the controls. This study therefore suggests evidence of a double origin for androstenedione secretion, from the testes and probably from the adrenals.     

Patterns of development of gonads, sex-drive and hormonal responses in tropical beef bulls

The development of different traits was studied in tropical beef bulls of seven genotypes (Brahman, Africander, British and combinations of these) from approximately 500 to 910 d of age. Bulls were raised under pasture conditions without supplementation. At each examination, approximately 2 mo apart, bulls were weighed, palpated (including scrotal and testicular measurement), electroejaculated, and subjected to two libido tests with estrus-induced females. At alternate examinations, plasma luteinizing hormone (LH) was measured at 30 and 150 min post gonadotrophin releasing hormone (GnRH) injection (LH - 30 and LH - 150) and testosterone (T) was measured at 150 min (T - 150). In general, nutritional and environmental stressors appeared to impede bull reproductive development. Scrotal circumference increased nonlinearly, apparently influenced by puberty and average daily gain (ADG). Libido increased overall, albeit nonlinearly also. No apparent marked differences in development of either trait could be attributed to genotype differences, although Brahman bulls tended to display lower sexual interest. The LH-30 level was relatively high (>14 ng/ml) at 500 and 640 d of age, but then dropped markedly at 760 d followed by a slight recovery. The LH-150 level followed a similar pattern, although it was very low at 500 d of age. The T-150 level showed a reverse pattern, being lower initially and higher in the latter part of the study. No apparent genotype differences occurred. Possible contributory influences on these patterns, including the onset of puberty and sexual maturity, season and nutrition, are discussed herein.     

Plasma estradiol concentrations and effect of HCG on plasma estradiol and testosterone in normal subjects and patients with endocrine disorders.

Plasma estradiol concentrations were determined by radioimmunoassay in various endocrine disorders using antiserum to estradiol-17beta succinyl bovine serum albumin. Clinical significance and diagnostic value of plasma estradiol were assessed in hypothalamic-pituitary, adrenal and gonadal disorders. In general, estradiol concentration was correlated well with the degree of sexual maturity and was of great diagnostic use. Plasma estradiol in females mainly originated from the ovary, while the testis is the principal source of estradiol in males. The adrenal gland seemed to play a minor role as a source of estradiol at least in normal males and females. The role of estradiol in gynecomastia and in liver disease was also investigated. More than a half of the cases with gynecomastia had elevated concentrations of plasma estradiol, which probably explains the pathogenesis of this manifestation. Cirrhotic patients showed frequently hyperestrogenemia probably due to delayed disappearance of estradiol. In the study of stimulation with human chorionic gonadotropin (HCG), 3,000 IU daily for three days in ten normal men, the peripheral concentrations of esradiol showed maximum and fourfold increases 24 hours after the 1st injection of HCG. The testosterone levels, on the other hand, increased stepwise and reached a maximum of about two times preinjection levels 24 hours after the 3rd injection. In gonadal disorders, HCG produced various patterns of plasma estradiol and testosterone in accordance with the gonadal conditions and dissociated response patterns of both sex hormones were frequently found. The determination of plasma estradiol was useful in the study of the function of not only the ovary, but also the testis and the simultaneous measurement of plasma estradiol and testosterone after HCG administration presented interesting informations about pathophysiology of gonadal disorders.     

Proteins secreted by the sheep conceptus suppress induction of uterine prostaglandin F-2 alpha release by oestradiol and oxytocin

In Exp. I, 0.5 mg oestradiol or vehicle (0.5 ml absolute ethanol + 0.5 ml 0.9% NaCl) was injected i.v. at 08:00 h on Day 14 (onset of oestrus = Day 0). Blood samples were obtained via a jugular catheter at 30 and 1 min before oestradiol and every 30 min for 10 h afterwards. Plasma was obtained and assayed for 15-keto-13,14-dihydro-PGF-2 alpha (PGFM) by radioimmunoassay. Before oestradiol, PGFM basal values were higher (P less than 0.01) in pregnant (N = 10) than nonpregnant (N = 6) ewes (193 +/- 30 vs 67 +/- 8 pg/ml). However, at 4-10 h after oestradiol, pregnant ewes (N = 5) had less variable (P less than 0.01) PGFM values than did nonpregnant ewes (N = 5). In Exp II, conceptus secretory proteins (CSP) were obtained by pooling medium from cultures of Day-16 sheep conceptuses (N = 40). Ewes received 750 micrograms CSP + 750 micrograms plasma protein (N = 6) or 1500 micrograms plasma protein (N = 6) per uterine horn at 08:00 h and 18:00 h on Days 12-14. All ewes received 0.5 mg oestradiol at 08:00 h on Day 14 and blood samples were collected as in Exp. I and assayed for PGFM. On Day 15, 3 ewes in each group received 10 i.u. oxytocin and 3 received saline i.v. at 08:00 h and blood samples were taken continuously from 10 min before to 60 min after treatment. Mean PGFM response to oestradiol was suppressed (P = 0.05) in CSP- vs plasma protein-treated ewes (371 +/- 129 vs 1188 +/- 139 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Intraperitoneal injection of zymosan in mice induces pain, inflammation and the synthesis of peptidoleukotrienes and prostaglandin E2

Intraperitoneal injection of zymosan in mice induced rapid extravasation and accumulation of plasma protein in the peritoneal cavity. Neutrophils began to appear in the peritoneal cavity after a lag period of approximately 3 hours. The injected mice exhibited a pain response (writhing) during the first 30 minutes after injection, but writhing ceased before protein or cell accumulation had reached maximum levels. The injection of zymosan induced synthesis of PGE2 (measured by RIA) which reached maximum levels at 30 minutes, then declined slowly. Peptido-leukotriene levels (detected by bioassay, RIA and HPLC) increased rapidly after injection, reached a peak within an hour of injection and declined to undetectable levels within 4 hours. The early peptido-LT was predominantly LTC4, while later, LTE4 was the major component. LTD4 levels remained low throughout and no LTB4 was detected at any time. Indomethacin treatment elevated levels of peptido-LTs, reduced PGE2 levels and inhibited writhing. Phenidone reduced peptido-LT levels. In vitro studies demonstrated that zymosan stimulates LTC4 synthesis by peritoneal cells whereas LTE4, LTD4, LTB4 or monoHETES were not detectable (using HPLC methods). The source of enzymes responsible for the in vivo metabolism of LTC4 to LTD4 and LTE4 could not be identified.     

Effects of testosterone and 5alpha-dihydrotestosterone on luteal lifespan in dairy heifers

Endogenous concentrations of testosterone increase approximately 7 d prior to estrus in cattle and goats. Inhibition of testosterone synthesis results in a delay of luteal regression in both species. The purpose of this experiment was to determine if treatment with testosterone or 5alpha-dihydrotestosterone (DHT), 2 to 6 d prior to the endogenous rise in testosterone, would result in premature luteal regression. Sixteen heifers were randomly assigned to one of three treatment groups: 1) Control (n = 6); 2) testosterone (100 mug, n = 5); or 3) DHT (100 mug, n = 5). Each heifer received a single injection of the appropriate steriod on Day 8, 9, 10, 11 or 12 post estrus. Jugular venous blood samples were collected at frequent intervals for 24 h to quantify testosterone, and then daily for 14 d to quantify progesterone. Concentrations of testosterone increased within 15 min of injection of testosterone, and reached a maximum at 30 min. Concentrations were maintained at > 2 ng/ml throughout the first 24 h after injection. Based on concentrations of progesterone, neither androgen had any effect on the lifespan of the corpus luteum or the level of luteal function.     

蛋白激酶A对小鼠受精卵早期发育过程中M期促进因子活性的影响

为研究小鼠体内 1 细胞期受精卵M期蛋白激酶A(PKA)对M期促进因子 (MPF)活性的影响 ,应用PKA激动剂cAMP及热稳定性抑制剂PKI显微注射入 1 细胞期受精卵内 ,观察MPF及PKA活性变化 .未经注射的对照组MPF活性在分裂期增高 ,分裂间期下降 ;而PKA活性在进入分裂期下降 ,分裂间期升高 .cAMP组PKA活性维持高峰值 ,直至注射HCG后 2 8h ,MPF活性高峰延迟 30min出现 ;PKI显微注射组PKA活性低 ,而MPF活性在注射HCG后 2 7 5h即达高峰 ,且维持高峰时间达1 5h .结果表明 ,PKA活性在细胞周期中也呈波动性 ,间期活性高 ,分裂期活性低 ;PKA高活性抑制MPF活性 ,而抑制PKA活性则MPF活性高峰提前出现 .     

Pituitary and gonadal secretory responses of rams following intravenous infusion or injection of graded doses of GnRH

Four adult Romney rams were utilized in a study of LH and testosterone secretory responses following intravenous administration of GnRH by continuous infusions over 8 h (total doses were 12.5, 50 and 200 μg) or by single rapid injections (doses were 3.1, 12.5, 50 and 200 μg). In the former case infusions of sterile saline were made in control experiments. Blood samples were collected via jugular catheters at intervals during and for 7 h after GnRH infusion, and for 4 h following GnRH injection. Plasma LH and testosterone concentrations were measured by specific radioimmunoassays.Each infusion of GnRH resulted in the secretion of LH with peak levels being reached within 1 – 3 h of commencing the experiment, then levels decreased slowly despite continued infusion. Plasma testosterone levels rose subsequent to the LH elevation and continued to be elevated after completion of the GnRH infusion. Each GnRH injection resulted in a rapid and marked elevation of plasma LH concentrations to a peak within 15 – 20 min. Higher GnRH doses (50 and 200 μg) generally resulted in a second peak occurring approximately 1.5 – 2 h later. Testosterone levels rose subsequent to each LH elevation.     

The development of the mouse ovary and its response to exogenous gonadotrophins.

Immature mice aged 14 to 49 days were treated with a single injection of 4 i.u. HCG, or 3 i.u. PMSG followed 48 hr later by 2 i.u. HCG. After treatment with HCG alone the number of oocytes which were ovulated rose gradually from Day 21 to Day 28 and then remained constant, while the combined PMSG+HCG treatment induced a peak response between Days 24 and 28. The percentage of animals responding also varied with age and treatment. After the combined PMSG+HCG treatment, 90% of the animals ovulated on Day 21, while a similar proportion was not achieved in response to HCG alone until Day 32. The variation in response with age and treatment was related to follicular development within the ovary.     

Acute suppression of endogenous testosterone levels by exogenous testosterone in normal men

The effect of exogenous testosterone on endogenous plasma testosterone was studied in normal men. Intramuscularly administered testosterone-19,19,19-d3 rapidly appeared in the systemic circulation in large amounts. Endogenous plasma testosterone was suppressed to near-castrate levels. The suppressed level began to rise between 6 and 10 h, and reached a preinjection level at 24 h after the injection. Plasma LH decreased with a concomitant decrease in endogenous testosterone and began to rise as soon as plasma total testosterone returned to physiological levels.